(a) Field of the Invention
Embodiments of the present invention relate generally to flat panel displays. More specifically, embodiments of the present invention relate to an organic light emitting diode display and a method of manufacturing the same.
(b) Description of the Related Art
An organic light emitting diode display includes organic light emitting elements that each have a hole injection electrode, an organic light emitting layer, and an electron injection electrode. Each organic light emitting element emits light due to energy generated when an exciton generated by combining electrons and holes in the organic light emitting layer falls from an exited state to a lower state.
Since the organic light emitting element may deteriorate due to external factors such as external moisture, oxygen, or ultraviolet (UV) rays, it is desirable to seal the organic light emitting element. Further, it is often desirable for the organic light emitting diode display to have a small thickness or be easily bent, in order to apply the organic light emitting element to various applications. A thin film encapsulation (TFE) technology has seen recent use in the development of thin sealed organic light emitting diode displays. The thin film encapsulation technology often entails alternately laminating one or more inorganic layers and organic layers on the organic light emitting elements formed in a display region of a display substrate, to cover the display region with a thin film encapsulation layer. When the display substrate of the organic light emitting diode display having the thin film encapsulation layer is formed of a flexible film such as polyimide (PI), the display substrate is easily bent and useful for a reduction in thickness.
When the flexible organic light emitting diode display is bent, stress occurs. Specifically, tensile stress occurs toward the convex outer surface and compressive stress occurs toward the concave inner surface. A neutral plane NP at which no stresses are present occurs in an intermediate region between the inner and outer surfaces. Only when the organic light emitting element is positioned in the neutral plane are picture abnormalities avoided in the organic light emitting diode display.
However, when the thickness of the organic light emitting diode display is increased by internal and external films such as a polarizing film and a passivation film attached to the organic light emitting diode display, the tensile stress and the compressive stress are increased and the neutral plane becomes displaced. Accordingly, it is difficult to position the organic light emitting element in the neutral plane. Further, since the organic light emitting diode display has a layered structure made of complex materials, asymmetry of strains occurs due to a difference in tensile stress and compressive stress at the inner and outer surfaces of a bent bending portion. Accordingly, it is difficult to position the organic light emitting element in the neutral plane, thus giving rise to picture abnormalities.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention, and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.